You would find having such a need in most Yii Projects. Your database needs a specific format to store date fields, while you may want to display it in different formats to the users on forms and other views.
There came the need to perform two operations, always, on 'application boot' time. Example? My real world example involved some geo-location logic (that's the first operation) and syncing of some session details so KcFinder can be in sync with the user in context - each user with his own session container (the second).